1. Field of the Invention
This invention relates to a method for efficiently producing the articles having a joint structure consisting of a synthetic resin portion and a portion made of a porous elastic member, such as an air duct opening/closing damper adaptable in air conditioners for automobiles, by using a synthetic resin injection molding machine.
2. Description of the Prior Art
In order to give airtight sealing properties and an impulsive sound absorbing capacity (when the damper is closed) to said hard synthetic resin-made damper body, the idea of efficiently incorporating a porous elastic member such as soft polyurethane foam sheet has been proposed in Japanese Patent Application Kokai (Laid-Open) No. 24939/86.
This patent application shows techniques for forming a laminate damper according to which a sort of packing member comprising a soft foam sheet having bonded to its surface a sheet for preventing the extruded molten resin from permeation into said foam sheet is prepared, and a molten synthetic resin layer is laminated on the surface of said packing member to a desired thickness by using a resin extruder, followed by stamping molding to form an integral laminate. Also disclosed in this patent application is a sandwich structure comprising packing members laminated on both sides of a synthetic resin layer.
Said prior art techniques contribute to the simplification of the manufacturing process in that bonding of packing members is accomplished coincidentally with molding of the synthetic resin-made damper body by making use of the bonding properties of molten resin.
On the other hand, this technique still involves several problems to be solved such as mentioned below:
(a) The time required for the manufacturing is too long because of a series of steps involving stamping after extrusion of a molten synthetic resin onto the surface of packing member. PA1 (b) Although it is possible to make a planar laminate structure, it is difficult to obtain an article having a three-dimensional configuration. PA1 (c) Adhesive force between the soft foam sheet and the resin permeation preventive sheet made of paper or cloth tends to vary from product to product, and also the bonding strength between packing member and resin molding may prove unsatisfactory.
The present invention has for its object to provide an injection molding method for integral molding of a porous elastic member and a synthetic resin, which method is capable of substantially eliminating said problems of the prior art.